Table 1 Application of strategies to enhance recombinant protein production in E.Coli
Type of optimization | Optimization strategy | Specific optimization method | Application | References |
|---|---|---|---|---|
Regulating the RPs expression level | T7 RNAP transcriptional regulation | The promoter lacUV5 and lac were recombined to yield the promoter variants lac-1G. (A at the + 1 position was changed to G) | Over ten autolysis proteins were increased in yield. GDH activity was increased from 37.5 to 452.0 U/ml at 43 h | [20] |
T7 RNAP transcriptional regulation | Mutant LacI (V192F, does not bind IPTG) prevents leaky expression of T7 RNAP and dynamically regulates transcript levels | Three membrane proteins were increased in yield. E. coli cytosine transporter protein increased 4.5-fold at 6 h | [31] | |
T7 RNAP translational regulation | Rapid screening of suitable expression hosts using the base editor and CRISPR/Cas9 to construct an T7 RNAP RBS library | The expression level of a target gene in the variant strain library ranged from 28 to 220% of the parental strain. The GDH expression exhibited a 298-fold increase | [35] | |
T7 RNAP activity regulation | Single amino acid mutation in T7 RNAP (A102D), which reduced the ability to bind to the PT7 and decreased the RP production rate | Seven membrane proteins with varying degrees of production improvement (data not mentioned in the article) | [37] | |
T7 RNAP activity regulation | T7 RNAP was split into two fragments and expressed in tandem with a light-sensitive dimerization domain, which are functional activity under blue light | The expression intensity of mCheery was increased 80-fold under blue light irradiation compared to dark conditions | [43] | |
Plasmid expression regulation | Construction of an ITR library for pET-28a using degenerate primers and MEGAWHOP PCR, and rapid screening of mutants for strong transporter-competent signal peptides by β-lactamase | The multiple types of RPs (mAbs and human growth hormone (hGH)) were increased in yield. The yield of hGH reached 2.56 mg/L, a more than threefold increase | [51] | |
Plasmid expression regulation | Regulation of ColE1 plasmid replication-associated gene expression intensity using CRISPRi and the inducible promoter (Ptet) | The Plasmid libraries containing 1194 different copy numbers, increasing the yield of violacein | [53] | |
Balancing or decoupling the growth and production | Nutrient supplementation | Amino acids were supplemented according to the level of demand (refer to Sect. 3.1 for specific types and added content) | The production of pramlintide increased by 40% (protein concentration of 3.09 ± 0.12 g/L) | [24] |
Blocking the phosphotransferase system | Blocking the phosphotransferase system (PTS) by knockout ptsG or integration ptsG mutants. can effectively reduce the rate of glucose uptake and decrease the production of acetate | A variety of RPs were increased in yield, including eGFP (increased by 282%), vaccines (increased by 3.5-fold) and glutamate dehydrogenase (increased by 14.84%) | ||
Blocking the cellular stress response | Transcriptome analysis to identify genes associated with cellular stress response and knockout them. The blocking of CSR alleviates the down-regulated expression of a variety of growth-essential genes | The double knockout mutant BW25113ΔelaA + ΔcysW (DKO) had the highest activity in asparaginase production with 70.3 units/ml | [64] | |
Rare codon supplementation | Integrating six of the least abundant tRNA genes into the BL21(DE3) chromosome behind a ribosomal manipulator for expression | Increased yields of eight proteins, which have different lengths and rare codon contents | [13] | |
Blocking host growth | Induction of serine recombinase expression and knockout oriC (replication start gene) at late growth stages, blocking host growth | fivefold increase in RFP production | [80] | |
Inhibiting host growth | constructing a sgRNA library targeting growth-related genes, and 1332 different sgRNAs were screened to reduce host growth and increase GFP accumulation | GFP production increased more than fivefold when sibB/ibsB was inhibited | [82] | |
RPs Expression using o-ribosome | Construction of a specific 16S rRNA recognizing the RPs RBS site for translation | The yield of RPs is 6.3-fold higher than that of the wild type | [84] | |
Enhancing protein activity | Enhancing transit capacity to the periplasmic space | Enhanced TAT translocation pathway by overexpression of TatABC membrane protein. Meanwhile, the TAT translocation pathway was exploited by the signal peptide TorA fusion RPs | The yield of purified periplasmic hGH are 5.4 g/L | [92] |
Enhancing disulfide bond formation | a host called CyDisCo was developed by overexpressing sulfhydryl oxidase from the yeast mitochondria and disulfide bond isomerase from human cells | Efficient expression of DSB-rich RPs, including antibodies and therapeutic proteins. perlecan, a protein with 44 DSBs, can also be efficiently generated using this host | ||
Efficient glycosylation in the cytoplasm | Combination of ApNGT overexpression and various oligosaccharide synthesis pathways for cytoplasmic N-glycosylation | The various glycoproteins have been achieved,including glycoconjugate vaccines, multivalent glycopolymers and megadalton protein assemblies | [120] | |
Fusion solubilisation tag improves protein solubility | a variety of low-molecular-weight protein tags have contributed to the solubilization and yield enhancement of various RPs, requiring only fusion expression with recombinant proteins | The two growth factor fusions 6HFh8 tag can substantially increase the yield, reaching 9.7 and 3.4 g/L respectively | [129] | |
Overexpression of molecular chaperones | Select appropriate molecular chaperones for overexpression to improve folding efficiency, including GroES/GroEL, DnaK-DnaJ-GrpE, and co-expression | The overexpression of GroES/EL increased the solubility of polyunsaturated fatty acid isomerase from 29 to 97% and improved its specific activity by 57.8% | [133] |